1. Field of Invention
The present invention generally relates to dentistry, specifically to a method of making and using a surgical template for performing one or more dental implant osteotomies that can be molded directly in a patient's mouth or on a cast model.
2. Prior Art
In contemporary dental surgery, a prosthetic tooth is often used to replace a missing tooth. Typically, the prosthetic tooth is mounted on a dental implant that is secured in the jawbone of the recipient. The dental implant must be securely mounted in sufficient bone tissue so that it is as stable as a natural tooth root.
The conventional procedure for installing a dental implant includes performing an osteotomy, or drilling a hole in the maxillary (upper) or mandibular (lower) jawbone of the patient, inserting the implant in the hole, and attaching a prosthetic tooth to the implant. The dental implant is generally made of titanium or a high titanium alloy that can readily integrate with the recipient's jawbone.
The hole formed by the osteotomy must be located at a precise distance from adjacent teeth in order to guarantee a proper fit and cosmetic result for the prosthetic device. The hole must also be accurately located so that the implant is sufficiently anchored in the bone structure of the patient's jaw without causing injury to any vital structure, such as a nerve bundle.
Many techniques for locating the implant hole have been used in the past. It is known in dental surgery to make a cast model of the patient's mandible and/or maxilla in order to design or select the appropriate prosthetic device. Moreover, it is known to use a diagnostic tooth setup on the cast model to determine the most desirable tooth position in the final restoration. In locating and creating the hole for a dental implant, however, the most commonly used method is to survey the edentulous area (missing tooth space) visually and drill according to visual inspection. This free-handed technique is clearly not very precise because of the limited access and visibility in the patient's mouth, especially in the posterior region.
Other techniques for performing an osteotomy are available. U.S. Pat. No. 5,015,183 to Fenick (May 14, 1991) describes a method involving a casting having a radiopaque marker which is inserted in the patient's mouth. A series of x-rays are then taken to establish a trajectory for the proposed hole in the patient's jawbone. While the method provides an accurate means to locate the implant hole, it requires multiple x-rays, subjecting the patient to undesirable exposure levels, and is expensive and time-consuming.
U.S. Pat. No. 5,556,278 to Meitner (Sep. 17, 1996) describes a method and apparatus for locating an implant hole that has been commonly used by dental professionals for many years. This method involves creating a cast model of the patient's jaw and then placing a diagnostic tooth setup made from wax or other material in the edentulous space. A hole is then drilled through the diagnostic tooth setup into the jaw model. This hole corresponds to the prospective osteotomy in the patient's real dental arch and therefore the location and orientation of the hole will correspond to an optimum location and orientation of the implant osteotomy. A guide post, whose design and dimension can vary, is then inserted into the hole with a portion of it projecting from the base of the edentulous ridge. A guide sleeve is then slid over the projecting part of this guide post until the base end of the sleeve rests in contact with the cast arch.
A non-bonding, separating medium, such as wax, is then applied on the cast arch in the edentulous space and on the cast tooth surfaces wherever the template forming material will be applied. This procedure is used to facilitate the removal of the template from the cast model once the resin is cured, since most resins have a high degree of polymerization shrinkage when set. A template material, preferably a self-cured or light-cured resin material, is then applied to the cast arch around the sleeve in the edentulous space and around at least one tooth adjacent to each side of the edentulous space. Once the resin has completely cured, the template is trimmed to an appropriate size. It is then inserted into the patient's mouth and the position and orientation of the guide sleeve can be radiographically visualized before the hole is drilled.
Dr. Frank Higginbottom describes an alternative but similar method of fabricating a surgical template, in Higginbottom, Frank, 2003 October, Fabrication of a Radiographic Guide and Surgical Template, Step-by-Step Instructions by Institut Straumann, Switzerland. In this procedure, a guide post is also secured-into the patient's cast model first. However, instead of applying a self- or light-cured resin, a thick resin sheet is placed onto the entire cast model and vacuum-formed under high-powered suction from a vacuum former combined with high heat, usually in excess of 149° C. (300° F.). Excess material below the height of the contour of the adjacent teeth is then trimmed away. A significant amount of time is required to trim away the excess material because the resin sheet is vacuum-formed over the entire model. Further, unless all the undercuts of the model have been adequately blocked out by a separating medium, the model is frequently damaged or destroyed during the removal of this resin layer due to the thermal shrinkage of the resin material.
While the Meitner and Higginbottom methods provide relatively accurate means to locate an implant hole, their templates are complicated to fabricate and cannot be directly made in a patient's mouth. The setting and hardening process of the resin usually involves a physical and/or chemical change that is not reversible, and in the event of a mistake, the whole resin application step must be repeated. Further, in practice these procedures are very time consuming due to the multiple steps, equipment, and materials involved in fabricating the template. Particularly, the process of applying the separating medium and the resin (self-cured, light-cured, or vacuum-formed), and the removal, trimming, and polishing of the hardened resin usually takes significant amounts of time even with a trained hand.
U.S. Pat. No. 5,989,025 to Conley (Nov. 23, 1999) describes a drill guide apparatus for use in preparing a dental implant site comprising a tubular drill guide with an external screw thread, a stent with an external screw thread, and an attachment part that removably attaches to the drill guide. The screw threads enable the tubular drill guide to be removably engaged with the stent. The attachment part also has screw threads which are complementary to the screw threads of the tubular drill guide and can function as a radiographic marker or for other purposes. The problem with this approach is that there are a number of small removable parts and attachments that a patient may accidentally swallow or inhale during surgery. Further, it is difficult for the surgeon to manipulate various removable attachments while performing the intended osteotomy.
U.S. Pat. No. 5,775,900 to Ginsburg et al. (Jul. 7, 1998) describes a thermally deformable clear acrylic resin removable prosthetic stent which is configured to form a full or partial removable prosthesis. The stent becomes moldable when heated to above 49° C. (120° F.) for a few minutes. The stent may then be formed on a model of the patient's teeth or intraorally. Once formed and chilled, the stent becomes stable and can be used as a surgical and radiographic stent. However, this stent comprises only a clear acrylic resin and does not enable the use of any drill guide which is critical for providing an accurate means to locate an implant hole and to guide the drill in the right direction when performing the intended osteotomy. Further, the operator must first perform the extra steps of mixing a plasticized methyl methacrylate liquid monomer with a methyl methacrylate polymer powder, and then curing the mixture at high pressure (68.9–137.9 bar or 1000–2000 psi) and high temperature (145° C.–155° C.) for four to eight minutes in order to produce the moldable acrylic resin.
Others have recently described surgical templates that are fabricated using advanced computer technologies. For example, U.S. Pat. No. 5,967,777 to Klein et al. (Oct. 19, 1999) describes a surgical template assembly having one or more drill guides and one or more dental implant guides which are precisely located via a computer-driven milling machine. The method involved comprises the steps of fitting a CT (computerized tomography) scan appliance to a patient's mouth, obtaining CT scan data of the patient's jawbone and the CT scan appliance, and computer generating an image of the patient's jawbone from the CT scan data and a simulation of a dental implant. This method requires the operator to possess specialized computer and technological skills beyond those of an average dental professional, and is both very expensive and time-consuming.
While some of the above discussed methods will locate the implant hole with good accuracy, their templates are complicated and time-consuming to fabricate, and usually require numerous steps, equipment, and materials. The newer advanced computer technologies used in making the template also require the operator to possess specialized training and skills. Alternatively, many dental surgeons in the past have opted to go to dental laboratories to fabricate the template according to the older methods, rather than do it themselves. However, these laboratories charge a relatively high fee to fabricate the template and ultimately result in a longer wait for the patient to finally receive a customized template for the osteotomy.
Thus existing surgical templates for performing dental implant osteotomies are not user-friendly. These templates are complicated, require many steps, equipment, and materials to fabricate. These templates are also not easy to operate.
Objects and Advantages
It is accordingly a principal object of one aspect of the invention to provide an improved method of fabricating a template and an improved template for performing dental implant osteotomies. Further objects are to provide such a template which allows an operator to quickly fabricate a surgical template manually, either directly in a patient's mouth or on a cast model in minutes using hot water alone, without going through the numerous and tedious steps in making a traditional vacuum-formed or cured resin template, or spending a significant amount of money for a commercial laboratory to fabricate the device.
Yet further objects of other aspects of the invention are to provide a surgical template consisting of at least one rigid drill guide that provide an accurate means to locate the implant hole and to guide the drill in the correct orientation when performing the intended osteotomies; to provide a surgical template for performing osteotomies having at least one drill guide securely locked in a thermoplastic base, thus creating a strong one-piece device to prevent a patient from accidentally swallowing or inhaling loose parts or attachments during surgery; to provide a surgical template with a thermoplastic base that can reversibly soften in heated water into a malleable material that can be remolded and adjusted by hand without additional tools so that should a mistake occur, the operator can make corrective adjustments easily; to provide a surgical template with a variety of pre-molded base sizes to provide the best custom fit for the intended patient and further to minimize trimming of excess base material and to provide better visibility during surgery; and to provide a surgical template that requires no advance technical or computer knowledge from the operator so that any person skilled in the art of dental surgery can quickly learn to fabricate and operate this device.
Still further objects of other aspects of the invention will become apparent from a consideration of the ensuing description and drawings.